No strobe needed for "Wagon Wheel" Reverse Rotation effect

Where do you live that they use 30 Hz electricity?

Um... when and where have you seen this?

I've heard it discussed, but *never* have seen it myself.

I've watched airplane propellors, looking for just this effect. Nuthun! We do see changing highlights if either the plane or ourselves are moving (so the angles are changing.) That's not a strobe effect.

But the only time I've seen any strobe effects in airplane propellors are on TV shows and in movies. I suspect that many people remember seeing the effect in the past, but don't realize that they're remembering a movie or TV show.

High contrast objects are needed for the effect to

No airplane is needed! Go right now an make a white disk with a bolt down the center, chuck it in an electric drill, then draw propellors or whatever on it. Spin it in sunlight at various speeds and carefully observe. Do you see any "strobe" effects? I only see a grey disk.

The Wikipedia article mentions some effects, but they appear when the object's motion is creating very obvious flashes (such as 10Hz) which might stimulate motion detectors for either direction. But such an effect will not create "strobe" phenomena where an illusory object slows to a stop, then reverses its rotation.

I think the key is that it occurs for reflective objects (like metal) being in a position to reflect the sunlight directly at your eyes. I.e., you see glare from a reflective surface or edge only when it is in a certain position during it's rotation. Essentially just as Bill has said in other posts.

For an airplane propeller, I imagine the effect would produce a stationary image IF you and the plane are stationary. For a moving strobe-like image, you or the plane would have to be moving so that the angle of the sun--airplane--your eyes is shifting.

Of course, what we really need to do is see the effect for ourselves sometime in the near future, and maybe even think of ways to test our different hypotheses.

Regards,

Mark

But Miller accounted the full-turn effect =E2=80=93 maybe in his own way, and you account the full-turn effect with an outward elegance. But Miller also selected the systematic error, but on the other you introduced the error of the first turn is subtracted from the data of first turn contained errors and masking effects the same as others.

Subtracting, you on one hand as if selected the systematic error, but on the other you introduced the error of the first turn into the data for markers 180 degrees apart.

This gives 8 , and 8 independent of differences in ), shown in Fig. 10 >>, you proceed from the idea that Miller had to obtain ideal . Factually such symmetry is basically impossible, the more that the degrees of turn have been measured not with the accuracy you would need.

Another pesky robot!!!! Take no notice.

John, thanks for confirming my suspicions.

Mark

Weird.

Hey, two more interesting effects:

A car behind me in the adjacent lane was close enough that I could observe one hubcap in the rear-view mirror. I could see a very obvious stroboscopic effect, and the entire hubcap appeared to be rotating slowly. But at the same time there was no strobe effect when the same hubcap was viewed in the side mirror. The road was rough enough that the rearview mirror was vibrating, and tiny bright highlights on objects appeared as short lines rather than points. But the side view mirror didn't show the same effects.

While I was passing a truck with the rising sun exactly behind us, there was a completely unmoving shadow of lug nuts visible on the inner surface of the truck lug nuts. An accidental Zoetrope! The Zoetrope was formed by the slots between lug nuts, so when the wheel spun rapidly, sunlight shining between these slots was swept in one direction while the lug nuts on the other side of the circle were moving in the opposite direction. Oddly, the lugnut shadows on the wheel showed about twice as many lug nuts as there should have been, and they appeared squashed (so the shadow of each nut looked tall and narrow.)

Using my spinning disk with stuck-on nuts, I see a similar effect when I hold the edge close to my eyes and look through the spinning slots. I see blurry images of the nuts on the other side of the circle, and they are sitting still. They do appear to be rotating in place though!

((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer snipped-for-privacy@chem.washington.edu UW Chem Dept, Bagley Hall RM74 snipped-for-privacy@eskimo.com Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http//amasci.com

Nah. Its probably some trucker with a set of spinning rims on his rig. ;-)

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ c (velocity of light in a vacuum) = 1.8x10^12 furlongs per fortnight

Air wrenches are cheap! Think of a number and halve it, twice. Compressed air is no problem: trucks have on-board compressors for the brakes.

unless they're an owner operator they'll probably be calling a tyre guy.

Bye. Jasen